Deceitful Jelly and the Gift of Colours

Christmas is imminent, and one of the stimuli in this week’s issue is of reactions to an unusual gift – glasses that allow people with a form of colour-blindness to perceive some colours for the first time. The other stimulus is also on the theme of perception, involving tricking the senses with servings of jelly which are not what they seem – so you might be able to philosophise under the pretext of a Christmas treat!

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Stimulus 1 – The Gift of Colours

This video is one of many that show colour blind people seeing new colours for the first time, after putting on EnChroma glasses.

It’s a good video for generating questions. There are the obvious themes of gift-giving, how we see the world, whether colours are real, and so on. The boy obligingly asks the question, “Is this the real world?” There is, however, another layer offered by the experiencing of watching a video of people watching someone having the intense emotional experience of seeing colours for the first time.

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I have normal vision. So, initially, I can see what he cannot. But when he puts the glasses on, he is having an experience that I can never experience: the magic of seeing the world with new eyes. I cannot know what that is like, but I can more easily imagine how he feels, because his emotional reaction triggers a sympathetic reaction in me.

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It’s an interesting exercise in the philosophy of mind. We each have a perception of the world, which we generally assume is shared. But colour-blindness reminds us that each of our perceptions is a separate world of its own. Yet our capacity for empathy crosses that separation, allowing us to feel as another feels even when we can’t see as they see.

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Possible questions include:

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Are colours real?
Can you feel what someone else feels?
Is it possible to see the world in a new way?
How much do we know about what it’s like to be someone else?

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The Science Bit

Around 5-8% of males and .5% to 1% of women have some form of colour-blindness (it’s mostly carried on the X chromosome, hence the sex disparity). The three types of cones that sense colour in the eye respond to different wavelengths, but there is some overlap in their sensitivity. In some forms of colourblindness, that overlap is too great. The glasses filter out some wavelengths, tidying up the signals sent to the brain so that more colours can be distinguished.

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Stimulus 2 – Deceitful Jelly

This alternative stimulus is all the more powerful because it is something the children can experience directly. Make some lemon-flavoured jelly and divide into three batches. Add some orange food colouring to one batch and some red colouring to another. Split each batch into jelly dishes or, better, glasses, so that you end up with one of each colour for each table.

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Give out one colour of jelly at a time, and get the children to taste each in turn, and to write down marks out of 10 for how much they like it, and how they would describe the flavour. Logistically, it’s easiest if you have a load of spoons so that they can use a fresh spoon for each one. One caveat – use vegetarian-friendly jelly and check any allergy advice around food colourings.

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Afterwards, you can reveal that all of them are exactly the same flavour. Generally, the expectations built by their sight will overrule the flavour perception, as when wine experts were famously fooled into talking about “cherries”, “cedar” and “chicory” when tasting a white wine dyed red. There may be some indignant disbelief, and you might have to do a “blind” tasting to prove it.

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Possible questions include:

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Is seeing believing?
When should you trust your senses?
What can you trust?
Do we see the world as it is, or do we make it up as we think it is?

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The Science Bit

The neural pathways for vision are faster than those for taste/flavour, and like other primates our colour vision is more developed than that of many other mammals, so we can discriminate between far more colours. As a species, we are very visual creatures; and our senses are far more integrated with one another than we might imagine. Sight tends to win over hearing too, as with the auditory illusion, the McGurk Effect, beautifully explained in this BBC video. https://www.youtube.com/watch?v=G-lN8vWm3m0